JPH04261277A - Flyback transformer - Google Patents

Abstract

PURPOSE:To prevent deterioration in video picture quality of a cathode ray tube caused by ringing by devising the circuit such that a harmonic generated at the secondary winding is eliminated through a ringing elimination circuit without fail. CONSTITUTION:The circuit is provided with a high voltage correction circuit 9 correcting a high voltage output drop fed to an anode of a cathode ray tube 5 from a high voltage terminal of a high voltage coil 3. Moreover, a ringing elimination circuit 1 is provided to a path (a) through which a harmonic generated in the high voltage coil 3 passes. Thus, even when the high voltage correction circuit 9 to apply a correction voltage to the secondary winding of the flyback transformer is connected in this way to the secondary winding, harmonic generated in the secondary winding passes through the ringing elimination circuit 1 without fail and is eliminated therein, and the deterioration in video picture quality of the cathode ray tube 5 caused by ringing is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flyback transformer equipped with a ringing removal circuit.

0002

2. Description of the Related Art FIG. 7 shows a conventional general flyback transformer circuit in which a ringing removal circuit 1 is provided. As is well known, the flyback transformer includes a low-voltage coil 2 and a high-voltage coil 3, boosts the flyback pulse applied from the low-voltage coil 2 side, and supplies the high-voltage output voltage to the anode of the cathode ray tube 5 via the high-voltage rectifier diode 4. In addition to Generally, when a flyback transformer is driven, harmonics with a frequency much higher than the fundamental wave of the flyback pulse are generated on the high-voltage coil 3 side due to distributed capacitance and leakage inductance on the high-voltage coil 3 side, and this harmonic is This spreads to various parts of the circuits of the television receiver and display device, causing a vertical striped pattern of light and darkness to appear on the screen of the cathode ray tube, resulting in a problem of deterioration of image quality. In order to solve this ringing problem, in recent flyback transformers, a ringing removal circuit 1 consisting of, for example, a coil and a resistor connected in parallel is connected to the low voltage end side of the high voltage coil 3, and the ringing removal circuit 1 is connected to the low voltage end of the high voltage coil 3. The circuit 1 removes the harmonics and prevents deterioration of image quality due to ringing.

0003

[Problem to be Solved by the Invention] As is well known, when a video signal is applied to a television receiver or a display device, or the brightness is adjusted in a brighter direction, a high voltage is output from the high voltage coil 3 to the cathode ray tube 5. Current flows, resulting in a drop in the high-voltage output voltage, causing distortion of the video screen of the cathode ray tube 5 and deterioration of focus.In order to solve this problem, recent high-voltage circuits including flyback transformers A high-voltage correction circuit is provided for stabilizing the high-voltage output voltage by correcting the amount of drop in the high-voltage output voltage when the high-voltage output current flows.

[0004] As this high voltage correction circuit, there is a method of controlling the drive current of the low voltage coil 2 in response to the amount of drop in the high voltage output voltage, but a method of controlling the drive current of the low voltage coil side (primary side) is based on the response. In addition to the poor characteristics, there is a problem that the device becomes large due to the flow of a large amount of current.In recent years, a correction voltage that compensates for the drop in the high voltage output voltage has been applied to the high voltage coil side of the flyback transformer ( (secondary side), methods to stabilize the high voltage output voltage are being adopted.

However, in a circuit equipped with a high voltage correction circuit on the high voltage coil side, the winding start side of the high voltage coil 3 is
Even if the ringing removal circuit 1 shown in FIG. The problem arises that it appears.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to provide a circuit that applies a correction voltage to the high-voltage coil side (secondary side) of a flyback transformer. An object of the present invention is to provide a flyback transformer that can reliably remove harmonics and prevent deterioration in image quality due to ringing.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. That is, the present invention includes a high-voltage correction circuit that detects the amount of drop in the high-voltage output voltage applied from the high-voltage coil to the anode of the cathode ray tube, generates a correction voltage to compensate for the amount of drop in the high-voltage output voltage, and applies it to the high-voltage coil. The connected flyback transformer is characterized in that a ringing removal circuit is provided in the harmonic passage from the high voltage coil to the anode of the cathode ray tube.

[0008]

[Operation] In the present invention, when a drop in the high voltage output voltage occurs, a correction voltage to compensate for the amount of the drop is created by the high voltage correction circuit, and the correction voltage is applied to the high voltage coil side to stabilize the high voltage output voltage. Control takes place. Even if harmonics are generated on the high-voltage coil side during the operation of this circuit, the harmonics are effectively removed when they pass through a ringing removal circuit provided in the harmonic passage path leading to the cathode ray tube.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. In the description of this embodiment, the same parts as those of the conventional circuit shown in FIG. 7 are denoted by the same reference numerals, and the redundant explanation thereof will be omitted. FIG. 1 shows the configuration of a first embodiment of a flyback transformer according to the present invention together with a high voltage correction circuit. In the figure, the high-voltage correction circuit 9 includes a high-voltage detection section 6 that detects the high-voltage output voltage applied to the cathode ray tube 5 from the high-voltage end side of the high-voltage coil 3, and a core 7 of the flyback transformer that is insulated from the high-voltage coil 3. an output transistor 10 that applies the addition voltage generated by the addition voltage generation coil 8 to the high-voltage coil 3 side by switching, and a high-voltage output voltage detected by the high-voltage detection section 6. Output transistor 10 depending on the amount of drop
a pulse width control circuit 12 that controls the pulse width of the ON period of the output transistor 1 via a drive transformer 11;
A multivoltage circuit 13 that amplifies a correction voltage applied from zero and applies it to the high voltage coil 3 side, and this type of high voltage correction circuit 9 is known from, for example, Japanese Patent Laid-Open No. 1-298873. , and its explanation will be omitted.

In this embodiment, a ringing removal circuit 1 is connected between the output side of the multiplier circuit 13 and the winding start end side of the high voltage coil 3, that is, the path through which harmonics pass. Cathode side of diode 4 and multiplier circuit 1
A capacitor 14 is connected between the output side of 3 and the output side of 3. In addition, ABL (Automatic
icBrightnessLimiter) side is taken out.

In the circuit of this embodiment, when harmonics are generated on the secondary side of the flyback transformer, the harmonics pass through the high-voltage coil 3, the ringing removal circuit 1, and the capacitor 14 in this order through the path a, and then reach the cathode ray tube 5. flows to Therefore, since the harmonics always pass through the ringing removal circuit 1, the harmonics are removed at that time, and it is possible to reliably prevent image quality from deteriorating due to ringing.

In the circuit shown in FIG. 1, the ringing removal circuit 1
is provided between the output side of the multiplier circuit 13 and the winding start side of the high voltage coil, but if this ringing removal circuit 1 is provided in the path through which harmonics generated on the secondary side pass, It may be provided in other circuit parts, for example, it may be provided between the winding start side of the high voltage coil 3 and the capacitor 14 as in the second embodiment shown in FIG. In this case as well, since the harmonics generated on the secondary side flow through the route a, they always pass through the ringing removal circuit 1, and the harmonics that cause ringing can be reliably removed. Further, as in a third embodiment shown in FIG. 3, the circuit shown in FIG. 2 may be modified to provide a circuit in which the multiplier circuit 13 is provided on the high voltage end side of the high voltage coil 3. In this case as well, the harmonics always pass through the ringing removal circuit 1, and the harmonics can be effectively removed.

Furthermore, as shown in the fourth embodiment of FIG. 4, a capacitor 15 is interposed between the output side of the ABL and the output end of the ringing removal circuit 1, so that the correction voltage is rectified by the capacitor 15. It's okay. Also in this case, since the harmonics generated on the secondary side flow along the route a, they always pass through the ringing removal circuit 1, and the harmonics can be removed reliably. Furthermore, as shown in the fifth embodiment of FIG. In this case as well, the harmonics generated on the secondary side always pass through the ringing removal circuit 1, and the harmonics can be removed.

As shown in each of the above embodiments, when the circuit is configured to apply a correction voltage to the high voltage coil side of the flyback transformer, by providing the ringing removal circuit 1 in the path through which the harmonics pass, the harmonics can be removed. can be reliably removed, and deterioration in image quality due to ringing can be prevented in any circuit. In addition, in a circuit that applies a correction voltage to the secondary side of a flyback transformer, for example, as shown in FIG. In the circuit interposed between the high-voltage coil 3, the high-voltage coil 3, the capacitor 14, and the cathode-ray tube 5, the harmonics flow through route a, and the harmonics do not pass through the ringing removal circuit 1, but reach the cathode-ray tube through the route a. In this case, harmonics cannot be removed. Therefore, in order to remove harmonics, it is essential to provide the ringing removal circuit 1 on a path through which harmonics always pass.

[0015] The present invention is not limited to the above-mentioned embodiments, and may be implemented in various ways. For example, in the above embodiment, the ringing removal circuit 1 is configured by a parallel circuit of a coil and a resistor, but the ringing removal circuit 1 may be configured by a single resistor, or by connecting a resistor and a capacitor in parallel. etc., resistors, coils,
It can be configured in any form using circuit elements such as capacitors.

Furthermore, in each of the above embodiments, the multiplier circuit is
Although configured as a voltage doubler circuit, this multi-voltage circuit may be configured as a triple or higher voltage circuit, or may be omitted if there is no need to amplify the correction voltage.

[0017]

[Effects of the Invention] According to the present invention, even if a high voltage correction circuit that applies a correction voltage is connected to the secondary side of the flyback transformer, harmonics generated on the secondary side are always removed through the ringing removal circuit. Therefore, it is possible to reliably eliminate the inconvenience that the image quality of the cathode ray tube deteriorates due to ringing.

In this way, it is possible to prevent image quality deterioration due to ringing, and the high voltage correction circuit and ringing removal circuit can be provided on the secondary side of the flyback transformer without any problem. This is very advantageous since it is also possible to stabilize the output voltage.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a first embodiment of a flyback transformer according to the present invention together with a high voltage correction circuit.

FIG. 2 is a circuit diagram showing a flyback transformer according to a second embodiment of the present invention together with a high voltage correction circuit.

FIG. 3 is a circuit diagram showing a flyback transformer according to a third embodiment of the present invention together with a high voltage correction circuit.

FIG. 4 is an explanatory diagram showing a flyback transformer according to a fourth embodiment of the present invention together with a high voltage correction circuit.

FIG. 5 is a circuit diagram showing a flyback transformer according to a fifth embodiment of the present invention together with a high voltage correction circuit.

FIG. 6 is a circuit diagram illustrating a bad example in which a ringing removal circuit is provided on a path other than the path through which harmonics pass, and the ringing component cannot be removed.

FIG. 7 is a circuit diagram of a conventional general flyback transformer provided with a ringing removal circuit.

[Explanation of symbols]

1 Ringing removal circuit 3 High voltage coil 5 Cathode ray tube 9 High voltage correction circuit

Claims (1)

[Claims] Claim 1: Connected to a high voltage correction circuit that detects the amount of drop in high voltage output voltage applied from the high voltage coil to the anode of the cathode ray tube, generates a correction voltage to compensate for the amount of drop in the high voltage output voltage, and applies it to the high voltage coil side. A flyback transformer characterized in that a ringing removal circuit is provided in a harmonic passage path from a high voltage coil to an anode of a cathode ray tube.